Energy: Tofu Ingredient Could One Day Replace Highly Toxic Material in Solar Cells

Tofu's magnesium chloride is not only perfectly safe, it's also much cheaper than the poisonous substance currently used by solar companies.

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Compared to meat, tofu is a healthier, cheaper, and less environmentally damaging food protein, and now researchers have discovered it also contains an ingredient that could replace a highly toxic and costly substance found in about 90% of the solar cells used today.

The traditional substance, an important element in millions of solar panels, is cadmium chloride. Not only is it toxic and expensive, it requires complex safeguards when manufacturing solar cells and special disposal after solar panels are discarded.

Enter Jon Major of the University of Liverpool's Stephenson Institute for Renewable Energy. Major has discovered that magnesium chloride can be substituted for cadmium chloride in solar cells, and that it's equally effective in solar cells.

Magnesium chloride is extracted from seawater and is a common ingredient in aromatic bath salts and in foods such as tofu, and is used for melting ice on wintry roads. In other words, it so safe that people not only soak in it, they eat it as well.

By contrast, engineers applying cadmium chloride to solar cells must wear protective gear to prevent contact with the skin, eyes, and lungs. Cadmium chloride treatment also requires a rinsing step, and the water used for rinsing must be processed very carefully or it could find its way into the water table, then poison animals and people.

What's more, magnesium chloride is so easy to find that it costs only one-one thousandth of a US penny, compared with three-tenths of a cent for cadmium chloride.

One of the biggest problems with much renewable energy has been expense. "If renewable energy is going to compete with fossil fuels, then the cost has to come down," Major explained. "Great strides have already been made, but the findings in this paper have the potential to reduce costs further."

So far, the least expensive solar cells are based on a thin film of insoluble cadmium telluride. Alone, these cells convert less than 2% of sunlight into energy. By applying cadmium chloride to them, the panels' efficiency increases to over 15%. And Major's work shows that substituting magnesium chloride for cadmium chloride achieves the same efficiency.

"We have to apply cadmium chloride in a fume cupboard in the lab," Major said, "but we created solar cells using the new method on a bench with a spray gun bought from a model shop. ...Replacing [cadmium chloride] with a naturally occurring substance could save the industry a vast amount of money."

Asked why no one had previously thought of replacing cadmium chloride with magnesium chloride, Major said, "The only reason we can suggest is that cadmium chloride works well so it may be a case of 'if it's not broke, why is there a need to fix it?'"

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